"We know that marital problems have an impact on child functioning, and we know that sleep is a big problem for parents," said Jenae M. Neiderhiser, professor of psychology, Penn State.

New parents often report sleep as being the most problematic of their child's behavior. Neiderhiser and colleagues found that poor sleep patterns in children from ages 9 to 18 months are likely influenced by conflict in their parents' marriage, the researchers report in the current issue of Child Development.

Past research has shown a connection between marital distress and child sleep difficulty, but this study looks specifically at adopted infants and their families. By studying adoptive families, the researchers focused on environmental factors because there are no shared genetic factors if the child does not share genes with his or her parents. Infancy is a developmental period when sleep tends to become regulated.

"It is important to understand how parenting comes in to play here," said Neiderhiser. "Looking at the marital relationship is not direct parent-child interaction, but it is an index of stress in the family."

The researchers interviewed 357 sets of adoptive parents both together and separately, assessing their own habits and emotions as well as their children's behaviors. The parents were interviewed twice--first when their children were 9 months old, and again at 18 months.

Parents were asked a series of questions, such as "Have you or your partner seriously suggested the idea of divorce?"

Then they were asked to describe their child's behavior at bedtime, by rating several behaviors listed in the survey, such as "child needs parent in room to fall asleep" or "child struggles at bedtime."

The researchers showed that marital conflict in the first survey at 9 months predicted that the child would be more likely to have sleep problems at the time of the second survey at 18 months. However, if the child had sleep problems at 9 months, the parents were not more likely to have marital stress at 18 months.

"Research indicates that stress can negatively impact sleep," said Neiderhiser. "We also know that infancy is an important time for the development of sleep patterns. Our study suggests that marital instability is impacting change in the child's sleep patterns over time, and it could be that this is setting the child up for a pattern of problematic sleep. Hopefully the next part of the study will help to clarify that." This is a longitudinal study currently funded to follow these children through age 8.

The lead author of this study is Anne M. Mannering, Oregon State University. In addition to Neiderhiser, other study scientists are Leslie D. Leve, senior scientist and science director, Oregon Social Learning Center; Daniel S. Shaw, professor and department chair of psychology, University of Pittsburgh; Gordon T. Harold, chair in behavioral genetics and developmental psychopathology, University of Leicester, and Alexander McMillan Chair in childhood studies and professor of psychology, Director Centre for Research on Children and Families, University of Otago, New Zealand; Katherine H. Shelton, lecturer in psychology, Cardiff University; Rand D. Conger, distinguished professor of human development, University of California at Davis; Laura V. Scaramella, professor in psychology, University of New Orleans; and David Reiss, clinical professor in the Child Study Center, Yale University. The National Institutes of Health funded this study.